Limonene-containing herbicide compositions, herbicide concentrate formulations and methods for making and using same

ABSTRACT

Provided are methods, kits and compositions for killing, controlling or suppressing a plant by administering to surfaces of the plant a herbicide composition comprising a herbicidally effective limonene component and an emulsifying agent in an aqueous emulsion, wherein the composition has a pH greater than 5. Also provided are methods, kits and compositions for killing, controlling or suppressing a plant, comprising administering to surfaces of the plant a herbicide composition comprising a herbicidally effective limonene component and an emulsifying agent in an aqueous emulsion, wherein the composition includes a wetting agent. Also provided are methods, kits and compositions for killing, controlling or suppressing a plant, comprising administering to surfaces of the plant a herbicide composition comprising a herbicidally effective limonene component and an emulsifying agent in an aqueous emulsion, wherein the composition has a pH greater than 5 and includes a wetting agent.

BACKGROUND

This invention relates to improvements in the field of herbicidaltreatment of plants. The invention involves a method of herbicidaltreatment of plants whereby unwanted plants and grasses are terminatedusing a formulation that is highly effective to non-selectively kill.plants it contacts. More particularly, the invention relates to“knock-down” herbicide formulations that comprise a herbicidally activelimonene component.

By way of background, limonene is a naturally occurring chemical foundin high concentrations in citrus fruits and spices. Limonene, otherwiseknown as orange limonene or 1-methyl-4-(1-methylethenyl)cyclohexene or4-isopropenyl-1-methyl cyclohexene, occurs naturally in various etherealoils, particularly oils of lemon, orange, lime, grapefruit, caraway,dill and bergamot. It has a chemical formula of C₁₀H₁₆, a molecularweight of 136.2, and contains 88.1% Carbon and 11.8% Hydrogen by weight.The d-form of limonene is a liquid having a boiling point of 175.5-176degrees centigrade.

Some limonene is prepared by extraction from plants of the mint family,a large quantity is obtained from citrus oils, which are typically80-90% limonene, and some is obtained from pine oil. For example,d-limonene can be obtained from steam extraction of citrus peels oforange, Lemon, lime, grapefruit and bergamot. Some of the extractionscan contain as high as 90% d-limonene; however, to produce technicalgrades of d-limonene of higher purity, i.e., greater than about 95%,distillation of the oils is required. d-Limonene can also be synthesizedchemically. d-Limonene has a pleasant citrus scent and it can besuitably used in any living environment.

In addition to uses as flavor additives in a. wide variety of foods andbeverages and uses in perfume materials, d-limonene has also been usedin household and industrial cleaning products. It is readily availablefrom commercial sources such as Florida Chemical Company, Inc., and isavailable in three different grades, named untreated/technical grade,food grade and lemon-lime grade. The food grade comprises about 97%d-limonene, the untreated/technical grade about 95%, and the lemon-limegrade about 70%, the balance in each case being other terpenehydrocarbons and oxygenated compounds.

Limonene has become a valuable industrial chemical. It finds use as asolvent and cleaning agent (in the manufacture of synthetic pine oil),as an expectorant, as a wetting and dispersing agent, as a monomer inthe manufacture of various polymeric resins, as a flavorant in many foodproducts and a precursor in the synthesis of the flavorant carvone, andas a polymerization inhibitor in storage of the tetrafluoroethylenemonomer used in the manufacture of polytetrafluoroethylene (PTFE). It isalso used in many soaps and perfumes for its lemon-like flavor and odor.In addition, limonene is a registered active ingredient in at least 15pesticide products used as insecticides, insect repellents, and dog andcat repellents. For example, pesticide products containing limonene areused for flea and tick control on pets, as an insecticide spray, anoutdoor dog and cat repellent, a fly repellent tablecloth, a mosquitolarvicide, and an insect repellent for use on humans.

Limonene is of relatively low acute toxicity taken orally. The U.S. Foodand Drug Administration considers limonene Generally Recognized as Safe(GRAS) as a food additive or flavoring, and as a fragrance additive. TheU.S. Environmental Protection Agency has granted limonene an exemptionfrom the requirement of a tolerance when it is used as an inertingredient in pesticide formulations, and when used as an insectrepellent tablecloth.

Turning now to consideration of herbicides, a wide range of chemicalsare used to control weeds in the agricultural industry and to controlunwanted vegetation in the landscaping industry. The aim of herbicidesis to prevent weeds and unwanted plants from competing with a desiredcrop in the case of agricultural uses, or competing with preferredvegetation in landscaping applications.

At present, there are two main classes of herbicidal chemicals that areused in connection with terrestrial plants, which is the subject of thepresent invention. In particular, the herbicides are generally separatedinto those that have a “contact” action upon plants, and those that havea “systemic” action upon plants. Some herbicides have both a contact andsystemic action on plants. Other types of herbicides act in other ways,such as, for example as soil sterilants.

Herbicides may either be selective or non-selective. Selectiveherbicides, for example “Treflan” (trifluralin), may be utilized for theselective destruction of certain types of grass. Non-selectiveherbicides such as “Roundup” (glyphosate) may be used as a generalherbicide for destroying or controlling many different types of plantsand grasses.

A large number of herbicides and plant hormones have been developed overthe years. In the early days inorganic compounds such as sodium chlorateand sodium arsenite and various borate compounds were used. There werealso developed other organic herbicides such as Nphenylcarbamate,“Randox”, and other chlorinated phenoxy compounds. In addition,industrial waste products were quite common. Later on, the hormone typeweed killers 2,4-D (2,4-dichloro-phenoxyacetic acid) and 2,4,5-T(2,4,5-trichloro-phenoxyacetic acid) were developed, and have becomequite common. More complicated organic weed killers and proprietarychemicals such as “Network” or “Roundup” (both glyphosates) have alsobeen developed.

In many cases herbicides have deleterious effects. For example, they maypoison beneficial crops, affect other plants or animals, and/or poisonthe soil. In addition, many herbicidal compositions presently on themarket are highly toxic to humans and domestic animals. Most chemicalherbicides are dangerous to mankind and are therefore dangerous whenaccidentally inhaled and/or absorbed into human and animal tissue.Because of the widespread concern of the deleterious side effects ofcurrently available herbicides, and the problems associated withabsorption and ingestion into other living matter, there is much concernas to the long-term use of complex and highly dangerous chemicals,especially when they enter into the food chain. A herbicide having lowertoxicity is desirable.

There has been developed recently a relatively nontoxic herbicide whichhas fatty acids as its main constituents. This herbicide has asmothering effect on plants, however its efficacy is limitedparticularly in controlling perennial weeds. A further disadvantage isthat the fatty acids are not readily carried or emulsified within anappropriate carrier fluid or solvent, which lessens its overalleffectiveness due to the difficulties encountered in delivering theherbicide to plants.

It has been suggested recently that limonene can be used at a highconcentration as a knock-down herbicide. In U.S. Pat. No. 5,998,335 toSelga et al., knock-down herbicidal compositions are described, one ofwhich comprises about 95-96% by weight of d-limonene and about 4-5% ofother components. The '335 patent reports that when this composition wasapplied to vegetation as a fine droplet spray (targeting 60-80% coverageof vegetation), most vegetation showed visible signs of stress (e.g.,wilting or browning) within 2 to 24 hours of application of theherbicide. Selga et al. also reported in the '335 patent that anemulsified mixture of 60% d-limonene with water and commercialemulsifier was also tested. When this formulation was applied tovegetation as described above, most vegetation began showing visiblesigns of stress within 2 to 36 hours.

One disadvantage of the herbicides described by Selga et al. is thatsuch high concentrations and volumes of limonene would be costprohibitive and cumbersome for spraying large areas. These formulationsalso present practical challenges associated with effectively atomizingand spraying such oily or highly viscous compositions.

In light of the above, there is a continuing need forenvironmentally-friendly herbicides having increased efficiency andefficacy. The present invention addresses this need and provides a widevariety of benefits and advantages.

SUMMARY

In one form, the present invention provides a method for killing,controlling or suppressing a plant by spraying onto one or more leavesof the plant a liquid herbicidal composition including water, aherbicidally active limonene component, an emulsifying agent and a pHmodifier effective to provide a pH greater than 5. As will beappreciated by a person of ordinary skill in the art, limonene is acidicand when dissolved in water will lower the pH typically to range ofabout 4 to 5.

In another form, the invention provides a method for making a herbicidecomposition, the method including: (1) providing a liquid herbicideformulation, the herbicide formulation including a herbicidally activelimonene component and an emulsifying agent; (2) diluting theformulation with water to provide a herbicide composition; and (3)mixing into the herbicide composition a pH modifier effective to providea pH greater than 5. In alternative embodiments, the pH modifier can beprovided in the formulation with the herbicidally active limonenecomponent and emulsifying agent, or can be dissolved or dispersed in thewater prior to dilution of the formulation.

In yet another form of the invention, there is provided a kit fornon-selective burn down of plants. The kit includes a container havingtherein a liquid herbicide, the herbicide including water, aherbicidally active limonene component, an emulsifying agent and a pHmodifier effective to provide a pH greater than 5; and instructions,recorded in a medium, for applying the herbicide to a pre-selected areafor indiscriminately killing, controlling or suppressing plants growingin the area.

In still another form of the invention, there is provided a kit fornon-selective burn down of plants, the kit including a container havingtherein a liquid herbicide formulation, the herbicide formulationincluding a herbicidally active limonene component, an emulsifying agentand a pH modifier effective to provide a pH greater than 5; andinstructions, recorded in a medium, for diluting the formulation toprovide a herbicide composition. Also recorded in the medium in someembodiments are instructions for applying the herbicide composition to apre-selected area for indiscriminately killing, controlling orsuppressing plants growing in the area.

In another embodiment, the invention provides a kit for non-selectiveburn down of plants that includes a container having therein a liquidherbicide formulation, the herbicide formulation including aherbicidally active limonene component and an emulsifying agent; andinstructions, recorded in a medium, for diluting the formulation withwater and adding a pH modifier effective to provide a pH greater than 5.Also recorded in the medium in some embodiments are instructions forapplying the herbicide composition to a pre-selected area forindiscriminately killing, controlling or suppressing plants growing inthe area.

In another form, the invention provides a “knockdown” herbicidalcomposition effective against mature weeds including water, aherbicidally active limonene component, an emulsifying agent and a pHmodifier effective to provide a pH greater than 5.

In another aspect of the invention, there is provided a method forkilling, controlling or suppressing a plant, which includes providing aliquid herbicidal composition including water, a herbicidally activelimonene component, an emulsifying agent and a wetting agent; andspraying the herbicidal composition onto one or more leaves of theplant.

The invention also provides a method for making a herbicide compositionthat includes: (1) providing a liquid herbicide formulation, theherbicide formulation including a herbicidally active limonene componentand an emulsifying agent; (2) diluting the formulation with water toprovide a herbicide composition; and (3) mixing into the herbicidecomposition a wetting agent.

In another form of the invention, there is provided a kit fornon-selective burn down of plants that includes a container havingtherein a liquid herbicide, the herbicide including water, aherbicidally active limonene component, an emulsifying agent and awetting agent; and instructions, recorded in a medium, for applying theherbicide to a pre-selected area for indiscriminately killing,controlling or suppressing plants growing in the area.

In another embodiment of the invention, there is provided a kit fornon-selective burn down of plants that includes a container havingtherein a liquid herbicide formulation, the herbicide formulationincluding a herbicidally active limonene component and an emulsifyingagent; and instructions, recorded in a medium, for diluting theformulation and mixing in a wetting agent to provide a herbicidecomposition. Also recorded in the medium in some embodiments areinstructions for applying the herbicide composition to a pre-selectedarea for indiscriminately killing, controlling or suppressing plantsgrowing in the area.

A “knock-down” herbicidal composition effective against mature weeds isalso provided, the composition including water, a herbicidally activelimonene component, an emulsifying agent and a wetting agent.

In another aspect of the invention, there is provided a method forkilling, controlling or suppressing a plant, including: (1) providing aliquid herbicidal composition including water, a herbicidally activelimonene component, an emulsifying agent, a wetting agent and a pHmodifier effective to provide a pH greater than 5; and (2) spraying theherbicidal composition onto one or more leaves of the plant.

In another form of the invention, there is provided a method for makinga herbicide composition that includes: (1) providing a liquid herbicideformulation, the herbicide formulation including a herbicidally activelimonene component and an emulsifying agent; (2) diluting theformulation with water to provide a herbicide composition; and (3)mixing into the herbicide composition a wetting agent and a pH modifiereffective to provide a pH greater than 5.

The invention also provides a method for making a herbicide composition,the method including: (1) providing a liquid herbicide formulation, theherbicide formulation including a herbicidally active limonenecomponent, an emulsifying agent and a pH modifier effective to provide apH greater than 5; (2) diluting the formulation with water to provide aherbicide composition; and (3) mixing into the herbicide composition awetting agent.

In another aspect of the invention, there is provided a kit fornon-selective burn down of plants that includes a container havingtherein a liquid herbicide, the herbicide including water, aherbicidally active limonene component, an emulsifying agent, a wettingagent and a pH modifier effective to provide a pH greater than 5; andinstructions, recorded in a medium, for applying the herbicide to apreselected area for indiscriminately killing, controlling orsuppressing plants growing in the area.

Another kit for non-selective burn down of plants provided by theinvention includes a container having therein a liquid herbicideformulation, the herbicide formulation including a herbicidally activelimonene component, an emulsifying agent and a pH modifier effective toprovide a pH greater than 5; and instructions, recorded in a medium, fordiluting the formulation and adding a wetting agent to provide aherbicide composition. Also recorded in the medium in some embodimentsare instructions for applying the herbicide composition to apre-selected area for indiscriminately killing, controlling orsuppressing plants growing in the area.

Still another kit for non-selective burn down of plants provided by theinvention includes a container having therein a liquid herbicideformulation, the herbicide formulation including a herbicidally activelimonene component and an emulsifying agent; and instructions, recordedin a medium, for diluting the formulation with water and adding awetting agent and a pH modifier effective to provide a pH greater than5. Also recorded in the medium in some embodiments are instructions forapplying the herbicide composition to a pre-selected area forindiscriminately killing, controlling or suppressing plants growing inthe area.

In yet another form of the invention, there is provided a “knock-down”herbicidal composition effective against mature weeds including water, aherbicidally active limonene component, an emulsifying agent, a wettingagent and a pH modifier effective to provide a pH greater than 5.

Further objects, features, aspects, forms, advantages and benefits shallbecome apparent from the description and drawings contained herein.

While the actual nature of the invention covered herein tan only bedetermined with reference to the claims appended hereto, certain formsand features, which are characteristic of the preferred embodimentsdisclosed herein, are described briefly as follows.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a bar graph setting forth the wilting assessment results at 2and 24 hours from a field study of common grasses and broadleaves inturf conducted in November of 2004. Statistical analysis is by Duncan'sMRT (P<<0.05). Treatments with the same letter or letter combination arenot significantly different.

FIG. 2 is a bar graph setting forth the wilting assessment results at 2and 7 days from a field study of common grasses and broadleaves in turfconducted in November of 2004. Statistical analysis is by Duncan's MRT(P<0.05). Treatments with the same letter or letter combination are notsignificantly different.

FIG. 3 sets forth a plot of the data presented in FIGS. 1 and 2.

FIG. 4 is a bar graph setting forth the color assessment results at 2and 24 hours from a field study of common grasses and broadleaves inturf conducted in November of 2004. Statistical analysis is by Duncan'sMRT (P_(—)<0.05) Treatments with the same letter or letter combinationare not significantly different.

FIG. 5 is a bar graph setting forth the color assessment results at 2and 7 days from a field study of common grasses and broadleaves in turfconducted in November of 2004. Statistical analysis is by Duncan's MRT(P-0.05). Treatments with the same letter or letter combination are notsignificantly different.

FIG. 6 sets forth a plot of the data presented in FIGS. 4 and 5.

FIG. 7 is a bar graph setting forth results from a field study onlambsquarters conducted in Florida in January of 2005. Ratings are basedon 0 to 10 (no damage to dead). Statistical analysis is by Duncan's MRT(P<0.05). Treatments with the same letter or letter combination are notsignificantly different.

FIG. 8 is a bar graph setting forth results from a greenhouse study onlambsquarters conducted in Michigan in January of 2005. Ratings arebased on 0 to 100% (no damage to dead). Statistical analysis is byDuncan's MRT (P_(—)<0.05) Treatments with the same letter or lettercombination are not significantly different.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments describedherein and specific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any alterations and further modificationsin the described fluids, methods, devices or kits, and any furtherapplications of the principles of the invention as described herein, arecontemplated as would normally occur to one skilled in the art to whichthe invention relates.

It has been discovered that the effectiveness of limonene compositionsas non-selective, “burn down” herbicides can be significantly improvedby increasing the pH of the composition to a pH of greater than 5, byincluding a wetting agent in the composition, or both. Accordingly, thisinvention provides in one embodiment a method of killing, controlling orsuppressing a plant by administering to surfaces of the plant aherbicide composition comprising a herbicidally effective limonenecomponent and an emulsifying agent in an aqueous emulsion, wherein thecomposition has a pH greater than 5. In another embodiment, theinvention provides a method of killing, controlling or suppressing aplant by administering to surfaces of the plant a herbicide compositioncomprising a herbicidally effective limonene component and anemulsifying agent in an aqueous emulsion, wherein the compositionincludes a wetting agent. In yet another embodiment of the invention,there is provided a method of killing, controlling or suppressing aplant by administering to surfaces of the plant a herbicide compositioncomprising a herbicidally effective limonene component and anemulsifying agent in an aqueous emulsion, wherein the composition has apH greater than 5 and includes a wetting agent.

In this description of the invention, the term “herbicidal” or“herbicidally effective” refers to the quality of being effective tokill, control or suppress a plant when at least a minimum amount of theherbicide composition contacts the plant. The term “kill” as used hereinin relation to a herbicide means to cause the above-ground portion of aplant to irreversibly cease normal function, typically resulting inwilting and browning and/or necrosis of the normally green tissues ofthe plant. It is, of course, possible that a plant, particularly aperennial plant, that is killed within this meaning may “re-sprout” andproduce new growth. The term “control” as used herein in relation to aherbicide means that, in a treated area, the plants experience at leastabout 90% mortality. The term mortality” as used herein can refer to apercentage of individual plants in the treatment area that are killed,or a percentage of the total mass or total surface area of vegetation inthe treatment area that experiences wilting, bleaching, browning ornecrosis. The term “suppress” is used herein in relation to a herbicideto mean that, in a treatment area, the plants experience from about 40to about 90% mortality. Application of an inventive herbicidecomposition to the plant causes the plant, where contacted, to wilt,bleach, or brown, which results in necrosis of the leaf (“burn down” andoftentimes death of the plant.

Herbicide compositions in accordance with many preferred embodiments ofthe present invention are nonselective and non-systemic, and areeffective against almost any vegetation, specifically against commoncrop and garden weeds, both annual and perennial. They are “contactherbicides” in that their action results from contact with plantsurfaces rather than uptake by the plant. In addition, inventiveformulations are “knockdown” (i.e. fast acting, typically within severalhours) or “burn down” herbicides, which must be sprayed over asubstantial portion of the above-ground part of the plant in order tohave an optimal or desired effect. Conveniently, the herbicides areapplied as a fine droplet spray. In addition, it is believed thatinventive herbicides have optimal burn down effect in relatively warmtemperatures and relatively dry conditions (relative to averagetemperatures and moisture for a given location). The active ingredientof the present herbicidal compositions has the advantage of being anenvironmentally friendly, natural product, which is unlikely to causeenvironmental pollution or create toxicity problems for humans ordomestic animals.

While not to be bound by theory, it is believed that when a thin film ofthe herbicide composition covers all or a portion of the leaves andother green tissues of a target plant, the herbicidally active limonenecomponent, under conditions present in the composition, may break downor dissolve the waxy layers of the plant, thereby causing the plant tolose the ability to prevent the loss of moisture to the environment.Since limonene-containing oils are natural oils, the non-toxic aqueousherbicide compositions of the invention are environmentally acceptableand have little, if any deleterious effect on humans, wildlife andnon-target vegetation.

For purposes of clarity, the term “herbicide composition” is used hereinto refer to a liquid that is actually contacted with a plant, such asfrom a sprayer, to achieve burn down in accordance with the invention. Aherbicide composition of the invention can be made and provided to anend user as a pre-made (or .“pre-mixed” or “ready to spray”) herbicidecomposition in some forms of the invention. In other forms of theinvention, the herbicide composition can be mixed by the end user at ornear the place where the herbicide composition will be used by dilutinga herbicide concentrate formulation and optionally adding otheringredients. As used herein, the terms “herbicide formulation” and“herbicide concentrate” and “herbicide concentrate formulation” are usedinterchangeably to refer to a formulation of ingredients in accordancewith the invention that can be diluted with water, with the optionaladdition of other ingredients, to provide a herbicide composition. Thismanner of providing a herbicide concentrate formulation may bedesirable, for example, where vegetation covering a large area is to besprayed, for example, using commercial spraying equipment, and thus agreat volume of the herbicide composition is needed. In such a case, aherbicide formulation can be provided to an end user, optionallytogether in a kit, with instructions for mixing the formulation withwater, and perhaps other ingredients in or near the sprayer to provide aherbicide composition. Such herbicide formulations and herbicide kitsare described further herein, but attention is first given to herbicidecompositions of the invention.

In accordance with the invention, a non-selective, burn down herbicidecomposition includes a herbicidally active limonene component, anemulsifying agent and a hydrophilic solvent, preferably water, and thatincludes a wetting agent, or has a pH greater than 5, or includes awetting agent and has a pH greater than 5.

The herbicidally active limonene component includes limonene or alimonene derivative in sufficient amount that it is effective, when in aherbicide composition provided in accordance with the present invention,to kill, control or suppress plants that are contacted with a sufficientamount of the herbicide composition. A sufficient amount is consideredto be an amount contacting a sufficient surface of the plants to achievea desired result. The herbicidally active limonene component can be apure or substantially pure limonene or limonene extract, or amulti-component composition that includes limonene. In this regard, theherbicidally active limonene component can comprise an essential oilthat includes limonene, preferably at least about 8% limonene by weight.For example, the limonene can be provided in the form of a citrus oil, apine oil, eucalyptus oil or a tea tree oil, any of which can be theherbicidally active limonene component in accordance with the invention.

Furthermore, the herbicidally active limonene component can comprise amodified limonene, as long as the modified limonene has herbicidalactivity in accordance with the invention. For example, based upon workthat has been reported by others, it appears that oxygenation oflimonene to provide limonene oxide may improve water solubilitycharacteristics while maintaining similar burn-down functionalitycompared to unmodified limonene. Such modified limonene compounds arecontemplated by the present invention, and are expressly included withinthe meaning of the term “herbicidally active limonene component.”

In one preferred embodiment, the herbicidally active limonene componentcomprises a citrus oil, e.g. orange oil. In another preferredembodiment, the herbicidally active limonene component comprisesd-limonene derived from a citrus oil. The fraction of the citrus oilcomprising d-limonene can be separated off by vacuum distillation, orany other conventional separation process. d-Limonene is volatile, andis separated off in the distillate. The distillate is a highlyconcentrated composition of the d-limonene, comprising about 95-96% byweight of d-limonene and about 4-5% by weight of other components. Thisdistillate may be utilized in a herbicidal composition of the presentinvention.

Although it is possible to use unrefined citrus oil, instead of thevacuum distillate, as discussed above, vacuum distillation (or otherseparation process, such as steam distillation (azeotroping), solventextraction, supercritical extraction etc.) has the advantage ofseparating the herbicidally active ingredient from flavor components ofthe citrus oil. The flavor components then form a valuable by-product,which can be utilized in, for example, foodstuffs or pharmaceuticalcompositions.

Other terpenes, particularly monoterpenes, that have similar herbicidalproperties to limonene in formulations as provided herein are consideredequivalent to limonene for purposes of the present invention. Similarly,other natural oils having high terpene content and having similarherbicidal properties to the limonene-containing oils discussed above informulations as provided herein are considered equivalent to thelimonene-containing oils for purposes of the present invention. “Highterpene content” as used herein means those natural oils having aterpene content of at least 50 percent. It is preferable that thenatural oil contains at least 90 percent terpene. Such terpenes andterpene containing natural oils are expressly encompassed within themeaning of the term “herbicidally active limonene component” as usedherein.

When pure or substantially pure limonene is used in an inventiveherbicide composition, the herbicide composition preferably includesfrom about 8 percent to about 100 percent by weight of the limonene,preferably from about 12 percent to about 30 percent by weight and morepreferably from about 15 percent to about 25 percent by weight. It isunderstood by a person of ordinary skill in the art that a herbicidecomposition having a lower concentration of limonene can be used toachieve a similar response by spraying a higher volume of the herbicidecomposition on the plant (increasing the volume increases the amount oflimonene to which the plant is exposed).

When a terpene containing natural oil is used, the amount of the naturaloil in the herbicide will depend upon the amount of terpenes in thespecific oil used. In one embodiment, the herbicide composition includesfrom about 8 percent to about 100 percent by weight of such a naturaloil, preferably from about 12 percent to about 30 percent by weight andmore preferably from about 15 percent to about 25 percent by weight.

As discussed above, the remainder of the herbicide composition compriseswater (or optionally another hydrophilic solvent), one or moreemulsifying agents, and one or more of a wetting agent and a pHmodifier.

The emulsifying agent is preferably a non-toxic emulsifying agent, andcan be a surfactant or other emulsifying agent known in the art, or amixture of one or more thereof. The emulsifying agents employed shouldbe capable, when mixed with water and the herbicidally active limonenecomponent, of forming an emulsion, preferably a homogeneous emulsion.

Useful emulsifying agents include lauryl dimethyl amine oxide,polyoxypropylene, polyoxyethylene block copolymers alcohol ethoxylateand nonylphenol ethoxylate. Alternatively, the emulsifying agent can bea polyethoxylated castor oil. One such emulsifying agent is availablecommercially under the trade name of Alkamuls EL620 from Rhone PoulencCo. It is non-toxic to humans and animals and will not cause skin or eyeirritation. Other commercially available emulsifying agents that arenon-toxic, such as polyoxyethylenesorbitans supplied by ICI Americas orSigma Chemical Company, may also be suitably used for the presentinvention. In a preferred embodiment a polyoxyethylenesorbitanmonooleate such as Tween 80 may be used.

Surfactants such as anionic and nonionic surfactants are acceptableemulsifying agents for use in a herbicide composition of the presentinvention. Preferred anionic surfactants include salts of fatty acids,alkyl sulphates, alkyl ether sulphonates and alkyl aryl sulphonates.Preferred nonionic surfactants include silicone based and nonylphenolethoxylate surfactants. Examples of preferred surfactants include about10 percent sulfonic acid, about 6 percent to about 7 percent sodiumlaurel sulfate, from about 8 percent to about 12 per cent alcoholethoxylate and from about 1 percent to about 2 percent olefin sulfonate.

In general, the emulsifying agent should be present in an amountsufficient to render the herbicidally active limonene component misciblein the water or other hydrophilic solvent. Generally, the herbicidecomposition will contain from about 0.05 percent to about 10 percent byweight of one or more emulsifying agent, preferably from about 0.1percent to about 0.5 percent by weight and more preferably from about0.2 percent to about 0.4 percent by weight.

While an inventive herbicide composition will typically comprise anemulsion of a herbicidally active limonene component with water, aninventive composition can include another non-toxic hydrophilic solventinstead of or in addition to water, such as, for example, ethanol,dilute acetic acid solutions, and the like.

As stated above, in one embodiment of the invention, the herbicidecomposition has a pH greater than 5. In another embodiment, theherbicide composition has a pH of from about 5 to about 10. The pH ofthe naturally acidic limonene can be raised by including a pH modifierin the herbicide composition. Examples of pH modifiers that can beselected for use in connection with the invention include, withoutlimitation, potassium carbonate, sodium hydroxide and potassiumhydroxide. In one preferred embodiment, the pH of the composition canrange from about 6 to about 8. In another preferred embodiment, the pHrange of the herbicidal composition is from about 8 to about 10.

Thus, in certain preferred embodiments of the inventive, herbicidecompositions, which are suitable for application as a spray, includeabout 8% to about 100% w/w %, preferably about 12% to about 30% w/w %,and more preferably from about 15% to about 25% by weight of aherbicidally active limonene component; from about 0.05% to about 10%w/w %, preferably about 0.1% to about 0.5% w/w %, and more preferablyfrom about 0.2% to about 0.4% by weight of an emulsifying agent; a pHmodifier in an amount effective to maintain a desired pH in thecomposition; and the balance of water or other selected hydrophilicsolvent. In one preferred embodiment, there is provided a herbicidecomposition comprising a herbicidally active limonene component at aconcentration of at least about 8% w/w %, an emulsifying agent effectiveto dissolve or disperse the herbicidally active limonene component inwater, in an effective amount, a pH modifier effective to maintain a pHgreater than 5, and a hydrophilic solvent, preferably water.

In another embodiment of the invention, the herbicide compositionincludes a wetting agent effective to improve the wetting properties,and possibly also the penetration properties, of the herbicidecomposition. When a wetting agent is included in a herbicide compositionof the invention, the composition sprayed on the weeds or othervegetation can be applied at a lower rate (i.e., measured in gallons peracre) to achieve an equivalent result because the wetting agent causeseach droplet of the composition to spread over a greater surface area ofthe plant. When a wetting agent is absent, the composition sprayed on aplant must cover a significantly greater surface area of the plant toachieve a similar result.

Many wetting agents suitable for use in herbicides are known to a personof ordinary skill in the art, and are available commercially. Examplesof wetting agents that can be selected for use in connection with theinvention include, without limitation, nonylphenol ethoxlyate, andanionic, cationic and nonionic (including silicone based) surfactantsand methylated seed oil. Particularly preferred wetting agents aresilicone surfactants. In one preferred embodiment, the compositionincludes from about 0.02% to about 1.0% w/w % of a wetting agent. Inanother preferred embodiment, the herbicide composition includes fromabout 0.05% to about 0.5% w/w %, more preferably from about 0.1% toabout 0.2% w/w %, of a wetting agent.

Thus, in certain preferred embodiments of the inventive, herbicidecompositions, which are suitable for application as a spray, includeabout 8% to about 100% w/w %, more preferably about 12% to about 30% w/w%, and more preferably from about 15% to about 25% by weight of aherbicidally active limonene component; from about 0.05% to about 10%w/w %, more preferably about 0.1% to about 0.5% w/w %, and morepreferably from about 0.2% to about 0.4% by weight of an emulsifyingagent; from about 0.02% to about 1.0% w/w %, more preferably about 0.05%to about 0.5% w/w %, and more preferably from about 0.1% to about 0.2%by weight of a wetting agent; and the balance of water or other selectedhydrophilic solvent. In one preferred embodiment, there are providedherbicide compositions comprising a herbicidally active limonenecomponent at a concentration of at least about 8% w/w %, an emulsifyingagent effective to dissolve or disperse the herbicidally active limonenecomponent in water, in an effective amount, a wetting agent at aconcentration of at least about 0.02% w/w % and a hydrophilic solvent,preferably water.

In still another embodiment of the invention, the herbicide compositionincludes a wetting agent effective to improve the wetting andpenetration properties of the composition and has a pH greater than 5.In another embodiment, the herbicide composition, including a wettingagent, has a pH from about 5 to about 10. In yet another embodiment, thepH is from about 6 to about 8, and in yet another embodiment, the pH isfrom about 8 to about 10. Examples of wetting agents and pH modifiersthat can be selected for use in connection with the invention includethose described above as non-limiting examples.

Thus, in certain preferred embodiments of the inventive, herbicidecompositions, which are suitable for application as a spray, includeabout 8% to about 100% w/w %, more preferably about 12% to about 30% w/w%, and more preferably from about 15% to about 25 % by weight of aherbicidally active limonene component; from about 0.05% to about 10%w/w %, more preferably about 0.1% to about 0.5% w/w %, and morepreferably from about 0.2% to about 0.4% by weight of an emulsifyingagent; from about 0.02% to about 1.0% w/w %, more preferably about 0.05%to about 0.5% w/w %, and more preferably from about 0.1% to about 0.2%by weight of a wetting agent; a pH modifier in an amount effective tomaintain a pH greater than 5; and the balance of water or other selectedhydrophilic solvent. In one preferred embodiment, there are providedherbicide compositions comprising a herbicidally active limonenecomponent at a concentration of at least about 8% w/w %, an emulsifyingagent effective to dissolve or disperse the a herbicidally activelimonene component in water, in an effective amount, a wetting agent ata concentration of at least about 0.02% w/w %; a pH modifier effectiveto maintain a pH greater than 5, and a hydrophilic solvent, preferablywater.

The herbicide compositions of this invention can be prepared by entirelyconventional procedures known to those of ordinary skill in the art. Forexample, the compositions can be made by preparing an aqueous mixture ofthe water, the emulsifying agent and the herbicidally active limonenecomponent. The resulting mixture can then be agitated until a dispersionor emulsion is formed. In one manner of making a herbicide compositionaccording to the invention, each non-aqueous component can be addedserially into a container, with stirring, preferably for at least about10 minutes after the addition of each component before adding the nextcomponent. After all of the non-aqueous components are mixed, the batchis agitated for another 10 minutes and the water can be mixed in toprovide the herbicide composition. It can then be tested for qualitycontrol, filtered and filled into suitable containers for shipment,storage or immediate use.

The invention has been described thus far in terms of the finalherbicide composition, and inventive herbicides can be made, sold andshipped as ready-to-use solutions. It is understood, however, that anexcellent manner of providing a herbicide composition to an end user isby first preparing a concentrate formulation that is then diluted withwater or other hydrophilic solvent by the end user to provide aherbicide composition for application to target weeds or othervegetation. Thus, herbicide compositions in accordance with theinvention can be packaged as ready-to-use herbicides, or can be packagedas herbicide concentrate formulations. Where an inventive herbicide isto be used in a relatively small quantity, such as for home uses, theherbicide can be packaged in a conventional ready-to-use dispensingsystem. In contrast, when the end user is a farmer or professionalapplicator who intends to use the herbicide on a large area, it would bemore desirable to provide a herbicide concentrate formulation that isready for dilution. As used herein, the terms “formulation” and“herbicide formulation” are intended to refer to such a concentrate.

In one embodiment, the formulation includes a herbicidally activelimonene component mixed with an emulsifying agent. In this embodiment,the formulation, along with a pH modifier, a wetting agent, or both(which can be obtained separately or provided with the formulation in akit) are mixed with water or other hydrophilic solvent by the end user,for example, in a commercial sprayer. In another embodiment, the pHbuffering agent, the wetting agent, or both, are premixed with theherbicidally active limonene component and the emulsifying agent toprovide a formulation that can be mixed directly with water or otherhydrophilic solvent to provide a herbicide composition. of course, it isalso possible to provide all of the ingredients separately to an enduser, with instructions regarding mixing the ingredients together toprovide a herbicide composition or a herbicide formulation.

In a particularly preferred embodiment, the herbicide formulationincludes a herbicidally active limonene component mixed with anemulsifying agent, and is provided separately from the pH modifier, thewetting agent, or both. A person of ordinary skill in the art willappreciate that the function of the emulsifying agent is to emulsify theherbicidally active limonene component with water, and the amount ofemulsifying agent to include in a herbicide formulation or a herbicidecomposition is related to the amount of limonene in the formulation,irrespective of how diluted the limonene will be in the final herbicide,composition. Thus, whether the herbicide formulation is ultimately mixedwith water in a water-to-formulation ratio of, for example, 1:1, 3:1 orhigher, the amount of emulsifying agent per unit limonene can remainunchanged. In contrast, the amount of pH modifier that would desirablybe included in a herbicide composition can depend upon the volume andthe initial pH of water mixed with the formulation; and the amount ofwetting agent that would desirably be included in a herbicidecomposition is dependent upon the total volume of the herbicidecomposition. Therefore, the emulsifying agent can advantageously bemixed with the herbicidally active limonene component in a herbicideformulation, while the pH modifier and the wetting agent are desirablyadded at the time the herbicide formulation is mixed with water toprovide the final herbicide composition.

In certain preferred embodiments of the invention, there are providedherbicide formulations comprising a herbicidally active limonenecomponent at a concentration of at least about 8% (w/w %), and anemulsifying agent at a concentration of from about 0.5% to about 10%(w/w %). In another embodiment, a herbicide formulation is provided thatcomprises a herbicidally active limonene component at a concentration ofat least about 8% (w/w %), an emulsifying agent at a concentration offrom about 0.5 to about 10% (w/w %), and a pH modifier in an amounteffective to maintain the pH of the final herbicide composition above 5.In another embodiment, a herbicide formulation is provided thatcomprises a herbicidally active limonene component at a concentration ofat least about 8% (w/w %), an emulsifying agent at a concentration offrom about 0.5 to about 10% (w/w %), and a wetting agent at aconcentration of from about 0.2% to about 10% (w/w %). In yet anotherembodiment, a herbicide formulation is provided that comprises aherbicidally active limonene component at a concentration of at leastabout 8% (w/w %), an emulsifying agent at a concentration of from about0.5 to about 10% (w/w %), a wetting agent at a concentration of fromabout 0.2% to about 10 (w/w %); and a pH modifier in an amount effectiveto maintain the pH of the final herbicide composition above 5.

Said formulations can advantageously be mixed with water, and optionallyone or more additional ingredients, at or near the location where theend user intends to apply the herbicide composition to plants. Thus, theinvention provides in one aspect a method for making a herbicidecomposition that includes providing a liquid herbicide formulation, theherbicide formulation including a herbicidally active limonene componentand an emulsifying agent; diluting the formulation with water to providea herbicide composition; and mixing into the herbicide composition a pHmodifier effective to provide a pH greater than 5 in the composition. Inanother aspect, the invention provides a method for making a herbicidecomposition that includes providing a liquid herbicide formulation, theherbicide formulation including a herbicidally active limonene componentand an emulsifying agent; diluting the formulation with water to providea herbicide composition; and mixing into the herbicide composition awetting agent. In yet another aspect, there is provided a method formaking a herbicide composition that includes providing a liquidherbicide formulation, the herbicide formulation including aherbicidally active limonene component and an emulsifying agent;diluting the formulation with water to provide a herbicide composition;and mixing into the herbicide composition a wetting agent and a pHmodifier effective to provide a pH greater than 5. The invention alsoprovides a method for making a herbicide composition that includesproviding a liquid herbicide formulation, the herbicide formulationincluding a herbicidally active limonene component, an emulsifying agentand a pH modifier effective to provide a pH greater than 5 in theformulation; diluting the formulation with water to provide a herbicidecomposition; and mixing into the herbicide composition a wetting agent.

A herbicidal formulation made or selected in accordance with the presentinvention can also be packaged or otherwise provided together withadditional components in a kit. In one embodiment of the invention, akit for non-selective burn down of plants is provided that includes acontainer having therein a liquid herbicide formulation, the herbicideformulation including a herbicidally active limonene component, anemulsifying agent and a pH modifier effective to provide a pH greaterthan 5; and instructions, recorded in a medium, for diluting theformulation to provide a herbicide composition. In another embodiment,also recorded in the medium are instructions for applying the herbicidecomposition to a pre-selected area for killing, controlling orsuppressing plants growing in the area.

In another embodiment, a kit for non-selective burn down of plants isprovided that includes a container having therein a liquid herbicideformulation, the herbicide formulation including a herbicidally activelimonene component and an emulsifying agent; and instructions, recordedin a medium, for diluting the formulation with water and adding a pHmodifier effective to provide a pH greater than 5. In anotherembodiment, also recorded in the medium are instructions for applyingthe herbicide composition to a pre-selected area for indiscriminatelykilling, controlling or suppressing plants growing in the area.

In another form of the invention, there is provided a kit fornon-selective burn down of plants that includes a container havingtherein a liquid herbicide, the herbicide including water, aherbicidally active limonene component, an emulsifying agent and awetting agent; and instructions for applying the herbicide to apre-selected area for killing, controlling or suppressing weeds or otherplants in the area.

Also provided by the invention is a kit for nonselective burn down ofplants that includes a container having therein a liquid herbicideformulation, the herbicide formulation including a herbicidally activelimonene component and an emulsifying agent; and instructions, recordedin a medium, for diluting the formulation and mixing in a wetting agentto provide a herbicide composition. In another embodiment, also recordedin the medium are instructions for applying the herbicide composition toa pre-selected area for killing, controlling or suppressing plantsgrowing in the area.

In another form of the invention, a kit for nonselective burn down ofplants is provided that includes a container having therein a liquidherbicide, the herbicide including water, a herbicidally active limonenecomponent, an emulsifying agent, a wetting agent and a pH modifiereffective to provide a pH greater than 5; and instructions for applyingthe herbicide to a pre-selected area for indiscriminately killing plantsgrowing in the area. Another kit for non-selective burn down of plantsis provided that includes a container having therein a liquid herbicideformulation, the herbicide formulation including a herbicidally activelimonene component, an emulsifying agent and a pH modifier effective toprovide a pH greater than 5; and instructions, recorded in a medium, fordiluting the formulation and adding a wetting agent to provide aherbicide composition. Still another embodiment of the invention is akit for non-selective burn down of plants that includes a containerhaving therein a liquid herbicide formulation, the herbicide formulationincluding a herbicidally active limonene component and an emulsifyingagent; and instructions, recorded in a medium, for diluting theformulation with water and adding a wetting agent and a pH modifiereffective to provide a pH greater than 5.

In addition to inclusion of herbicide formulations in a kit, asdescribed above, the invention also contemplates providing a pre-made,complete herbicide composition with other components in a kit. Thus, inanother, form of the invention, a kit for non-selective burn down ofplants is provided that includes a container having therein a liquidherbicide, the herbicide including water, a herbicidally active limonenecomponent, an emulsifying agent and one or more member selected from awetting agent and a pH modifier effective to provide a pH greater than5; and instructions, recorded in a medium, for applying the herbicide toa pre-selected area for indiscriminately killing plants growing in thearea.

An inventive herbicide composition or herbicide concentrate formulationin accordance with the invention can be prepared to include a variety ofother beneficial ingredients in addition to the ingredients discussedabove. By “beneficial”, it is meant that the additional ingredientprovides some additional functionality, efficacy, quality or otherdesirable attribute the herbicide or herbicide concentrate. For example,the herbicidally active limonene component may be blended with other,cheaper, and somewhat less volatile oils to form effective herbicides.Various natural oils (such as cottonseed oil, soybean oil, rapeseed oil,sunflower oil, safflower oil, olive oil, coconut oil, coconut milk, cornoil, grape seed oil and peanut oil) have been reported by others to lacksignificant herbicidal activity; however, they can be blended with theherbicidally active limonene component of the present invention to formeffective herbicidal compositions.

One or more other ingredients may optionally be included in thecompositions of the invention in order to provide aesthetic or otherbeneficial properties thereto. Such optional ingredients are, forexample, antimicrobial agents, preservatives, deodorizers, coloringagents, fragrances, additional emulsifiers, additional solubilizers,corrosion inhibitors and additional solvents. The only requirement isthat for any particular composition such optional ingredients becompatible with the other ingredients present in the composition orformulation.

By way of example, optional ingredients that can be incorporated includethe following: an antimicrobial, such as, for example, phenoliccompounds such as ophenylphenol and o-benzyl [p-chlorophenol];quaternary ammonium compounds such as alkyl dimethyl benzyl ammoniumchloride, octyl decyl dimethyl ammonium chloride, dioctyl dimethylammonium chloride, didecyl dimethyl ammonium chloride and alkyl dimethylbenzyl ammonium saccharinate; a deodorizer, such as, for example,N-alkyl-N-ethylmorpholinium ethyl sulfate; and a corrosion inhibitor,such as, for example, mono- and triethanolamine, ammonium hydroxide,sodium molybdate, sodium benzoate and tetra sodium ethylenediaminetetraacetate.

Other optional ingredients, as well as the amounts of the optionalingredients that can be employed, can readily be determined by oneskilled in the art. For example, the phenolic and quaternary ammoniumantimicrobial agents generally will not exceed a concentration of about0.2 percent by weight in the final herbicide composition.

In order to provide a reasonable shelf-life to the herbicidecompositions, it is preferable that a preservative be added to thecomposition. One such suitable preservative is sodium benzoatecommercially supplied by Pfizer, Inc. Other commercially availablepreservatives used for preserving food, as would be known to those ofordinary skill in the art, may also be suitably used.

The beneficial agents described above, and many others, as would becontemplated by a person of ordinary skill in the art, are well known tothose skilled in the art and are available commercially.

In a further aspect, the invention provides a method for killing,controlling or suppressing unwanted plant growth, wherein a herbicidecomposition provided in accordance with the present invention is appliedto the unwanted plant or plants. The composition is then permitted toremain in contact with the plant, preferably the leaves of the plant,for a period of time sufficient to kill, control or suppress the plant.The time required for effective treatment of a given plant is dependentupon a variety of factors including, but not limited to concentration,spray coverage, pH of the herbicide solution, the species of the plant,the size/age/maturity of the plant, the availability of leaf surfaces orother green surfaces, and ambient conditions.

In an agricultural setting, spray applications with standard equipmenttypically use 20 to 35 gallons per acre for good coverage. Commercialelectrostatic sprayers can bring the rates down significantly to lessthan 10 gal/acre and still achieve good coverage. In one manner ofpracticing the invention, the method includes spraying the herbicide onthe area at a rate of from about 5 gal/acre to about 40 gal/acre. Inanother preferred manner of practicing the invention, the methodincludes spraying the herbicide on the area at a rate of from about 5gal/acre to about 35 gal/acre.

In a homeowner or professional landscaping setting, spray applicationson weeds are typically susceptible to runoff. Depending concentration ofthe herbicidally active limonene component in the herbicide compositionas well as the density and maturity/size of the weeds, the equivalentspray volume per acre could be from a couple of quarts to 100 gallonsper acre or more.

The invention will be further described with reference to the followingspecific Examples. It will be understood that these Examples areintended to be illustrative and not restrictive in nature.

EXAMPLE 1

Preparation of Herbicide Formulation

A herbicide formulation (MM-01) was prepared in accordance with theinvention to include 94.0 w/w % limonene with the following emulsifiers:1.3 w/w % Tergtol™ NP-8 (nonylphenol ethoxylate surfactant), 2.0 w/w %Tergitol™ NP-9 (nonoxynol 9.5 surfactant) and 2.7 w/w % Pluracol® P-425(polypropylene glycol surfactant). The resulting formulation contains88% limonene w/w %. For making a 100 gallon batch of this herbicideformulation, each component is added one by one and the mixture isstirred for 10 minutes after each addition and before adding the nextcomponent, to ensure complete and homogeneous blending of thecomponents. After all the components are mixed, the batch is agitatedfor another 10 minutes, tested for quality control, filtered and filledinto suitable containers.

Preparation of Herbicide Compositions

The formulation was diluted with water to a 3:1 ratio by volume,represented as water:herbicide formulation ratio, to provide a herbicidecomposition (22% limonene w/w %). It is estimated that the pH of the 3:1ratio composition was 4.5. The pH was lowered to 4 with lemon juice in afirst test batch and raised to pH 9 with potassium carbonate in a secondtest batch. In addition, a herbicide composition with the 3:1 ratio wasmodified by adding 0.05% silicone based surfactant (Silwet) in a thirdtest batch.

Protocol for Testing Herbicide Compositions

This field trial was conducted in Northern California during November,2004. Each of the herbicide compositions described above was sprayedonto postemergent plants with backpack spray equipment to ensure goodcoverage without runoff. Primary weeds evaluated were Bermuda grass,fescue, and strawberry clover.

Color and wilting ratings were taken at 2 hours, 1 day, 2 days, and 7days after treatment. Data collected for the test compositions werecompared to an untreated control (UTC) and an area of vegetation treatedwith Paraquat (Gramoxone®). This trial contained 3 reps per treatment(except the paraquat treatment which was a single strip). Treatmentswere randomly distributed within a rep. Color and wilting ratings weretaken at 2 hours, 1 day, 2 days and 7 days after treatment. Results areset forth in FIGS. 1-6.

Discussion

In this trial, in which all treatment received 3:1 ratios(water:limonene formulation), the plants responded very rapidly. Inbroadleaf plants, discoloration followed by necrosis, and blackening ofthe leaf tissue occurred within 2 to 4 hours. In grasses, the responsewas more gradual, and leaves tended to gradually change from green toyellow to brown.

All MM-01 treatments resulted in a visual, burn down response within 2hours. After Day 1, all MM-01 treatments were significantly different(P<0.05) from the untreated control (UTC).

The best MM-01 treatments were with 0.05% silicone surfactant and at pH9. At days 2 and 7, both were significantly better than the othertreatments. At days 2 and 7, the surfactant and pH 9 treatments werenumerically equivalent to the paraquat standard.

Wilting responses increased over time for all MM01 treatments. Colorratings for MM-01 did not change significantly over time.

The differences attributed to pH and surfactant are very apparent. Inthe 7 days after treatment, the impact of surfactant on wilting andcolor was tallied and the results are set forth in Table I below: TABLEI MM01 Effect 3:1 ratio MMO1 (3:1 Measured (pH 4.5) ratio) + 0.05%Difference Difference Wilting 2.67 3.33 0.66 24.7% Color 3.67 5.00 1.3336.2% Average differences 1.00 30.5%

At 7 days after treatment, the impact of pH on wilting and color wasalso tallied, and the results are set forth in Table II below: TABLE IIEffect pH 4 pH 9 Difference Difference Wilting 3.00 3.67 0.67 22.3%Color 3.33 4.67 1.34 40.2% Average differences 1.01 31.3%

The use of a nonionic, silicon surfactant increased the wilting ratingsby 24.7% and color by 36.2%.

The use of pH 9-increased the wilting ratings by 22.3% and color by40.2%.

EXAMPLE 2

A field trial was conducted in Zellwood, Fla. The same formulationdescribed in Example 1 was used in the Florida trial. All limonenetreatments were made at a 3:1 ratio by volume, represented aswater:herbicide formulation ratio, to provide a herbicide composition of22% limonene (w/w %). Four reps per treatment were used; all treatmentswere randomly distributed within a rep. The weed species was commonlambsquarters (1 to 2 feet in height). Treatments applied were pH 3, 7,8 and 9 with and without a silicone surfactant, Silwet; each treatmentwas sprayed until runoff. The commercial burn down standard, Gramoxone(paraquat) was included. Readings were taken at 1 and 2 hours, and 1, 3and 7 days. An immediate wilting of the lambsquarters was observed withall limonene treatments starting at 1 hour. Effects with Gramoxone(paraquat) were first observed on day 1 and improved by Day 3. After thefirst 2 hours limonene effects were stabilized. Results after 3 days areset forth in FIG. 7.

Large common lambsquarters are a difficult to control weed for limonene,making it a good candidate to evaluate difference caused by pH andsurfactants. Evaluating the effect of pH, pH 7 gave the best responsewith and without surfactant. Without surfactant, it was significantlybetter than pH 3.

Side by side comparisons with the surfactant can also be made. Althoughnot statistically significant, surfactant increased limonene activitywith almost every pH with an average increase of 6.1% (see Table) TABLEIII Treatment pH pH + Silwet Difference % Difference pH 3 3.7 4.3 0.616.2% pH 7 4.7 5.0 0.3 6.4% pH 8 4.3 4.7 0.4 9.3% pH 9 4.3 4.0 −0.3−7.5% Average differences 0.25 6.1

EXAMPLE 3

A series of trials were conducted at Michigan State University (MSU) inEast Lansing, Mich. to optimize the response with limonene on key weeds.Grasses responded strongly to limonene, which diminishes theirsuitability for pH and surfactant evaluations since all treatments gavean excellent herbicidal response. Mature common lambsquarters does notrespond well to limonene making it a good candidate for these trials.

The same formulation described in Example 1 was used in the MSUgreenhouse trials. Four reps per treatment were used. All limonenetreatments were made at a 3:1 ratio by volume, represented aswater:herbicide formulation ratio, to provide a herbicide composition of22% limonene (w/w %). The herbicide composition was applied in spraychamber designed to mimic an agricultural application. Spray volume was60 gallons per acre and the spray nozzle pressure was 40 psi. The weedspecies was common lambsquarters (1 to 2 feet in height). Treatmentsapplied were pH 3, 5, 7, 8 and 9 without any surfactant. A singlereading was taken at day 4. Results are set forth in FIG. 8.

There was a strong trend towards a pH response with pH 5 being theoptimal pH. pH 7 and 8 had numerically better responses than pH 3 (11.4%and 7.5% respectively) or unadjusted limonene at pH 4.2 (14.7% and 10.6%respectively). pH 9 was significantly lower than the other treatments.

All surfactants improved the performance of the limonene formulation inwater. The silicon based product, Sylgard, was significantly better bycomparison.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiments have been shown and described and thatall changes and modifications that come within the spirit of theinvention are desired to be protected.

1. A method for killing, controlling or suppressing a plant, comprising: providing a liquid herbicidal composition including water, a herbicidally active limonene component, an emulsifying agent and a member selected from the group consisting of a wetting agent, a pH modifier effective to provide a pH greater than 5, and a combination thereof; and spraying the herbicidal composition onto one or more leaves of the plant.
 2. The method according to claim 1 wherein said spraying comprises spraying in a manner whereby the herbicidal composition contacts at least about 60% of the surface area of the plant's leaf or leaves.
 3. The method according to claim 1 wherein the herbicidally active limonene component is present in the composition at a concentration of at least about 8%.
 4. The method according to claim 1 wherein the herbicidal composition includes water, a herbicidally active limonene component, an emulsifying agent and a pH modifier effective to provide a pH greater than
 5. 5. The method according to claim 4 wherein the composition has a pH of from about 5 to about
 10. 6. The method according to claim 4 wherein the composition has a pH of from about 6 to about
 8. 7. The method according to claim 4 wherein the composition has a pH of from about 8 to about
 10. 8. The method according to claim 4 wherein the emulsifying agent is a surfactant.
 9. The method according to claim 4 wherein the emulsifying agent is present in the composition at a concentration of from about 0.05% to about 10%.
 10. The method according to claim 4 wherein the emulsifying agent is selected from the group consisting of a nonylphenol ethoxylate surfactant, a nonoxynol surfactant, a polypropylene glycol surfactant and a mixture of any one or more thereof.
 11. The method according to claim 4 wherein the pH modifier is selected from the group consisting of potassium carbonate, potassium hydroxide and sodium hydroxide.
 12. The method according to claim 1 wherein the herbicidal composition includes water, a herbicidally active limonene component, an emulsifying agent and a wetting agent.
 13. The method according to claim 12 wherein the wetting agent is a silicone surfactant.
 14. The method according to claim 12 wherein the wetting agent is present in the composition at a concentration of from about 0.02% to about 1%.
 15. The method according to claim 12 wherein the wetting agent is selected from the group consisting of anionic and nonionic surfactants and a mixture of any one or more thereof.
 16. The method according to claim 1 wherein the herbicidal composition includes water, a herbicidally active limonene component, an emulsifying agent, a wetting agent and a pH modifier effective to provide a pH greater than
 5. 17. A method for non-selective burn down of plants, comprising: selecting an area having at least one plant growing therein; and spraying a liquid herbicide composition on the area, the herbicide including water, a herbicidally active limonene component, an emulsifying agent and a member selected from the group consisting of a wetting agent, a pH modifier effective to provide a pH greater than 5, and a combination thereof.
 18. The method of claim 17 wherein said spraying comprises spraying the herbicide on the area at a rate of from about 0.5 gal/acre to about 100 gal/acre.
 19. A method for controlling the growth of mature, unwanted plant(s), wherein a herbicidal composition including water, a herbicidally active limonene component, an emulsifying agent and a member selected from the group consisting of a wetting agent, a pH modifier effective to provide a pH greater than 5 in the composition, and a combination thereof, is applied to the unwanted plant or plants.
 20. A “knock-down” herbicidal composition effective against mature weeds including water, a herbicidally active limonene component, an emulsifying agent and a member selected from the group consisting of a wetting agent, a pH modifier effective to provide a pH greater than 5, and a combination thereof.
 21. A method for making a herbicide composition, comprising: providing a liquid herbicide formulation, the herbicide formulation including a herbicidally active limonene component and an emulsifying agent; and diluting the formulation with water to provide a herbicide composition; wherein the herbicide composition includes a pH modifier effective to provide a pH greater than
 5. 22. A method for making a herbicide composition, comprising: providing a liquid herbicide formulation, the herbicide formulation including a herbicidally active limonene component and an emulsifying agent; diluting the formulation with water to provide a herbicide composition; and mixing into the herbicide composition a wetting agent.
 23. A method for making a herbicide composition, comprising: providing a liquid herbicide formulation, the herbicide formulation including a herbicidally active limonene component and an emulsifying agent; diluting the formulation with water to provide a herbicide composition; and mixing into the herbicide composition a wetting agent and a pH modifier effective to provide a pH greater than
 5. 24. A method for making a herbicide composition, comprising: providing a liquid herbicide formulation, the herbicide formulation including a herbicidally active limonene component, an emulsifying agent and a pH modifier effective to provide a pH greater than 5; diluting the formulation with water to provide a herbicide composition; and mixing into the herbicide composition a wetting agent. 